1. Field of the Invention
This invention relates to a process for air-gap spinning para-aramid fibers wherein a certain combination of spinning process conditions has been found to result in increased fiber tenacity and elongation at break.
2. Description of the Prior Art
U.S. Pat. No. 3,869,429, issued Mar. 4, 1975 on the application of Blades discloses making para-aramid fibers using the so-called "air-gap" spinning process. That patent contains no recommendation of tension for washing; and teaches that drying can be conducted at tensions of less than 0.3 grams per denier, but cites "tensionless" as the only specific lower tension.
U.S. Pat. No. 4,016,236 and 4,560,743, issued Apr. 5, 1977 and Dec. 24, 1985 on the applications of Nagasawa et al. and Fujiwara et al. disclose making aramid fibers by air-gap spinning wherein the spun fibers are carefully dropped onto a netted belt for washing and drying in order to assure that the fibers are not subjected to any substantial tension in either of those operations.
U.S. Pat. No. 4,859,393, issued Aug. 22, 1989 on the application of Yang et al. discloses making para-aramid fibers of increased fatigue resistance by air-gap spinning into a coagulation bath having a temperature of at least 20 C., washing the fibers under a tension of 0.2 to 0.35 gpd, and drying the fibers at a lesser tension of 0.05 to 0.2 gpd.
European Patent Application Number 118,088, published Sep. 12, 1984 on the application of Satoh et al. teaches making para-aramid fibers of improved fatigue resistance whereby the fibers are passed from a coagulating bath to a chamber under reduced pressure.